This is the Asian citrus psyllid, a mottled brown insect about 3 to 4 millimeters long, or about the size of an aphid. Widespread throughout Southern California, it is now found in 26 of the state's 58 counties. (CDFA Photo)

This is the Asian citrus psyllid, a mottled brown insect about 3 to 4 millimeters long, or about the size of an aphid. Widespread throughout Southern California, it is now found in 26 of the state's 58 counties. (CDFA Photo)

UC Davis chemical ecologist Walter Leal has just discovered the sex pheromone of the Asian citrus psyillid. He has also discovered the sex pheromones of a number of other insects, including moths (background). (Photo by Kathy Keatley Garvey)

UC Davis chemical ecologist Walter Leal has just discovered the sex pheromone of the Asian citrus psyillid. He has also discovered the sex pheromones of a number of other insects, including moths (background). (Photo by Kathy Keatley Garvey)